Transfer of tumor specific immunity with "immune" RNA: prospects for the treatment of human cancer

Ribonucleic acids extracted from specifically sensitized lymphoid cells (I-RNA) have been shown to transfer specific immunoreactivity to normal non-immune lymphoid cells. Evidence for the transfer by I-RNA, of immune responses to tumor-associated antigens of animal and human neoplasms, in vivo and in vitro, is reviewed. Results obtained in our laboratory and in other laboratories indicate that xenogeneic, allogeneic and syngeneic I-RNA extracts mediate specific cytotoxicity to tumor cells, in vitro, and mediate transplantation resistance and tumor rejection responses in vivo. Our results suggest that I-RNA preparations fail to elicit immune responses directed against "self" antigens. By contrast, I-RNA's directed against "non-self" tumor-associated antigens appear to induce lymphocytes to effect specific anti-tumor immune responses. The mechanisms responsible for the failure of I-RNA to initiate immune responses against "self" antigens are not known at present and demand investigation. Preliminary results of a clinical Phase I trial of immunotherapy with xenogeneic I-RNA in selected cancer patients are reviewed. I-RNA might offer promise as a new modality for the immunotherapy of human cancer.